Weaving process for a high-density fabric on a water-jet loom

ABSTRACT

Process for producing high-density woven fabrics on a water-jet loom, comprising 
     feeding a warp having up to three catch threads on one edge, 
     inserting weft threads into the warp in the direction of the catch threads, 
     beating-up the weft threads to produce a woven fabric, 
     severing the ends of the weft threads at the edges of the warp, and 
     removing the ends of the weft threads, characterized in that, seen from both edges of the warp, 5 to 60 threads of the warp, following the catch threads on the edge of the warp with the catch threads, are support threads that are maintained at a tension that is 2 to 20 cN/tex higher than that of the threads forming the remaining warp, that after production of the fabric the weft threads between the edges of the remaining warp and the support threads are severed by fusion and joined to threads at the edges of the remaining warp, and that the severed ends of the weft threads are removed together with the support threads and the catch threads.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a process for manufacturing high-density wovenfabrics on a water-jet loom, and to a fabric produced using thisprocess.

Discussion of Related Art

A process of this type is known from EP-A-0,747,267, for example, andcomprises the following steps:

(a) feeding a warp having up to three catch threads on one edge,

(b) inserting weft threads into the warp,

(c) beating-up the weft threads in the direction of the catch threads toproduce a woven fabric,

(d) joint twisting of the catch threads to place the weft threads undertension,

(e) severing the ends of the weft threads, and

(f) removing the ends of the weft threads together with the catchthreads.

In producing high-density woven fabrics on a water-jet loom, it has beenobserved that the resulting fabric is looser at the edges than in theremainder of the fabric. The loose fabric edges make further processingof such fabrics difficult since the edges cannot be maintained under thesame tension as the remaining fabric. Fabric producers refer to this asslobby selvedges. This fluttering is particularly noticeable whenunrolling the fabrics or transferring them to another roll. Thefluttering of the fabric edges becomes more pronounced as the fabricwidth increases.

To contend with this fluttering, high-density fabrics are normallyproduced in widths of at most 1.6 m. However, producers of airbagsdesire fabric widths of at least 1.7 m, and especially 2 m, sincecutouts for manufacturing an airbag can then be made with minimum waste.

Frequently, high-density woven fabrics are coated after production withsilicone, for example. The fluttering edges prove disadvantageous in thecoating process as well and render uniform coating of the fabric almostimpossible.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a process as initiallydescribed, in which the aforementioned disadvantages are at leastreduced. In particular, the weaving process is to be such that thefabric produced is easier to handle in follow-on processing. It is alsoan object of the invention to provide high-density fabrics that are easyto handle.

FIG. 2 represents a water-jet weaving machine as used in the presentprocess including hot knives 7 and 8, severed ends of the weft andsupport threads 9, support threads 10, base structure 11, warp 12, warpbeam 14, tensioning means 18, first harness mechanism 24, second harnessmechanism 26, water jet nozzle 28, weft thread 30, reciprocating reed31, cutting means 34, catch cord 36, catch plate 38, vacuum line 40,twister 42, support brackets 52 and produced fabric 70.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of the thread routing to measure the static frictionof two different threads against each other in accordance with thepresent invention.

FIG. 2 represents a water-jet weaving machine used in the presentprocess.

DESCRIPTION OF PREFERRED EMBODIMENTS

According to the invention, the warp employed consists of catch threads,support threads, and the threads of the remaining warp. The warptherefore contains a total of four thread groups. These thread groupsoccur in the following order from one edge of the warp to the other inthe direction of weft insertion:

(i) support threads,

(ii) threads of the remaining, actual warp,

(iii) support threads, and

(iv) catch threads,

wherein the catch threads, support threads, and threads of the remainingwarp have different functions during the weaving process.

Surprisingly, it has been observed that when adhering to theseconditions, the fabric edges have properties that are at leastapproximately the same as those of the remaining fabric. Handling ofthe. fabric produced according to the invention is considerablyimproved. Fluttering of the warp edges is rarely observed.

High-density woven fabrics in the context of the present invention arethose in which the thread density is especially high in both the warpand weft directions and approaches the thread density achievable withthe respective loom. For example, the resulting high-density wovenfabrics have thread counts of 26 to 30 threads per cm when using threadswith a yarn titer of 235 dtex, 18 to 28 threads per cm with a yam titerof 350 dtex, and 17 to 25 threads per cm with a yam titer of 470 dtex.The thread counts cited here apply in particular to plain weaves and areadjusted accordingly for other weaves. A common factor for theseadjustments is the cover (kappa) factor.

The process of the invention succeeds particularly well if the distancesbetween adjacent threads, including the support and catch threads, isthe same over the entire width of the warp. Thus, the distance betweentwo different thread groups is also the same as the distance betweenadjacent threads in the same group.

In the process of the: invention, it is advantageous if the supportthreads are fed to the edges of the warp by separate sectional warpbeams onto which the support threads have been wound as a yarn sheet. Inthis manner, the tension required for the support threads can beadjusted particularly advantageously, by procedures that are known.

As a rule, it is sufficient if there is a yam sheet with 10 to 40support threads on each edge of the warp.

It has proven particularly advantageous if the support threads areselected with a hot-air shrinkage, measured at 190° C., of 1% to 4%, andpreferably 1% to 3%. Surprisingly, such threads allow an adjustment ofthe support thread tension required for the process of the inventionthat is particularly simple and uniform for all threads.

The process of the invention succeeds particularly well if twistedthreads are used as the support threads. It has proven especiallybeneficial if the support threads have 200 to 700 turns per meter. Theuse of double-twisted threads as support threads is recommended.Double-twisted threads are those in which a multi-filament yarn is firsttwisted and then two or more of such twisted multi-filament yarns are inturn twisted together. For the second twisting as well, it isadvantageous for the twisted multi-filament yams to have 200 to 700turns per meter. Twisting of the twisted multi-filament yarns in thedirection opposite the twist of the multi-filament yarns is recommended.

The process of the invention succeeds particularly well if supportthreads are selected that have a thread/thread friction between the weftand support threads of 20 to 70 cN.

The thread/thread friction is measured as follows: A Rothschild (Zurich)R-1188″F meter″ and R-1083″F meter winder″ are used. The principle formeasuring the static friction of a thread against itself is described insections 5.5 and 5.10 of the F meter user's manual.

To measure the static friction of two different threads against eachother, the measurement arrangement was modified slightly. The rollsnumbered 1, 2, 4, 5, and 6 in the drawing and the thread tension meter 7are components of the F-meter winder. Roll 3 was added. The drive forroll 6 can be regulated and takes up the measured thread at a rate of 10mm/min.

The thread routing is indicated by the figure. One thread (F1, solidline) is loaded with a freely suspended 10 cN weight G1 and routed fromthe right side over roll 4, from the left side over roll 5, past threadtension meter 7, and once around roll 6, and is then secured to the axisof the latter. The second thread (F2, dashed line) is also loaded with a10 cN weight G2 (freely suspended) and routed from the left side overroll 1. Thread F2 is then wrapped around thread F1 four times toward theright and then routed to the left again prior to thread F1, yielding 3 ½turns. Thread F2 is routed under roll 2 and over roll 3 to take-up roll6, where it is secured as for thread F1. For the threads F1 and F2, alength is selected such that weights G1 and G2 are suspended about 1 mbelow the measurement apparatus.

The motor (not shown) for roll 6 is now turned on. After 2-3 minutesrunning time to align the threads, thread F1 is positioned in the threadtension meter. The measurements are displayed on the R-1188 F meter andrecorded on an ABB Goerz SE 120 plotter. The force determined in thismanner is used as a measure of the thread/thread friction.

It is important for the weft threads to be severed by fusion. Severingby fusion is commonly known. In this case, the thread is heated at onelocation to a temperature at least equal to, but generally higher than,the thread melting temperature. In the simplest case, a wire heated tohigh temperature can be used, against which the weft thread ispositioned, heated until molten, and severed by moving it further. As arule, the wire is heated to a temperature that renders it red-hot.However, a heated knife can also be used, such as described in EP-A-0747 267 for severing the weft threads at the catch threads.

It is advantageous for severing by fusion to take place such that theends of the weft threads in the molten state adhere to the threads atthe edges of the warp. The molten end of the weft thread is used toattach the weft thread to at least one edge thread of the warp. In thismanner, a particularly stable warp edge is attained, which significantlyimproves the handling of the fabric produced.

It is especially beneficial if severing by fusion is performed such thatthe ends of the weft threads are fused in the molten state with thethreads at the edges of the warp. This severing by fusion can beperformed such that edge threads of the remaining warp that are adjacentto the hot severing element are also heated to the melting point, sothat a continuous weld is produced along the edges of the finishedfabric and plays a role in avoiding the aforementioned fluttering of theselvedges.

The object of the invention is also satisfied by a woven fabricproducible using the process of the invention. The fabric of theinvention differs from fabrics produced using the conventional weavingprocess on water-jet looms in that the weft threads are severed on bothedges of the fabric, while the weft threads in fabrics conventionallyproduced on water-jet looms are severed on only one edge of the fabricand protrude somewhat from the fabric on the other edge. In particular,when employing severing by fusion at the fabric edges, the fabricsproduced using the process of the invention are distinguished fromconventional fabrics produced on water-jet looms by the welds runninglongitudinally along both edges. The feel of the fabric of the inventionin the edge region is at least nearly the same as the feel between theedges, such as in the center of the fabric.

The fabrics of the invention are excellently suited for producingairbags, parachutes, and sailcloths, and for all applications in whichextremely dense woven fabrics are required. For example, yarns with anoverall titer of 470 dtex can be woven at a density of up to 25 threadsper cm in the warp and weft directions.

The invention will now be explained in more detail on the basis of thefollowing example:

EXAMPLE

A warp with a width of 207 cm, consisting of nylon-6,6 threads, was fedto a water-jet loom. Each thread of the warp had an overall titer of 470dtex and 72 filaments. The hot-air shrinkage of these yarns, measured at190° C. after heating for 5 minutes, was 8.2%.

Two yarn sheets, consisting of 40 nylon-6,6 threads and each wound on asectional warp beam, were also fed to the water-jet loom such that theywere adjacent to the edge threads of the warp in the reed of the loom.These yarns acted as support threads and had an overall titer of 234dtex and 68 filaments. The supportthread yarns were double-twistedthreads according to a Z 476 S 637 scheme. This scheme is realized byinitially twisting a yarn with 34 filaments in the S direction with 637turns per meter, and then twisting two yams, previously twisted in thismanner, in the Z direction with 476 turns per meter. The support threadshad a hot-air shrinkage of 1.8%, measured under the same conditions asthose for the hot-air shrinkage of the warp yarns.

Furthermore, the usual 4 catch threads for water-jet looms were fedoutside the yarn sheet of support threads, which was opposite theweft-insertion jet of the water-jet loom.

The weft thread employed was a nylon-6,6 multi-filament yarn with anoverall titer of 470 dtex and 72 filaments. The weft threads had ahot-air shrinkage of 8.2%. The thread/thread friction between the weftand support threads was 47.5 cN.

The threads of the warp, the support yarn sheet, and the catch threadswere introduced adjacently into the reed of the water-jet loom, wherebythe reed had 100 openings per 10 cm and two threads were drawn into eachreed opening. The warp threads were maintained at a tension of 120cN/tex and the support threads at a tension of 123 cN/tex.

A woven fabric was produced using the yarns thus described. The catchthreads were twisted to place the weft threads under tension and removedby suction, after severing the weft threads outside the support threads,together with the severed weft thread ends. The resultant fabric wasthen further processed by directing a red-hot wire between each of thesupport threads and the respective outermost thread of the warp,severing the weft threads and fusing them with the outermost threads ofthe warp. This resulted in a weld that could be felt along each edge ofthe warp.

The fabric produced in this manner had 21.5 threads per cm in the warpdirection and 21.5 threads per cm in the weft direction. The two edgesof the fabric had the same feel as the fabric interior. When rolling thefabric from one beam to another, the fabric remained taut even into theedge regions, and the slobby selvedges known to those skilled in the artwas not observable. This fabric also lent itself to particularly uniformcoating with an aqueous silicone dispersion over the entire width of thefabric.

What is claimed is:
 1. A process for producing a high-density wovenfabric on a water-jet loom, comprising: (a) feeding a warp having up tothree catch threads on a first edge and having a second edge opposite tothe first edge, (b) inserting weft threads into the warp, (c) beating-upthe weft threads in the direction of the catch threads to produce awoven fabric, (d) jointly twisting the catch threads to place the weftthreads under tension, (e) severing the ends of the weft threads, and(f) removing the ends of the weft threads together with the catchthreads, using 5 to 60 warp threads as support threads following thecatch threads on the first edge of the warp, using 5 to 60 warp threadsas support threads on a second edge of the warp, maintaining the supportthreads at a tension that is higher than the threads forming remainingwarp, severing the weft threads located between the edges of theremaining warp and catch threads by fusion, joining the edges of thesevered weft threads to the edges of the remaining warp, and removingthe severed ends of the weft threads together with the support threads.2. The process according to claim 1 comprising the additional step ofsetting a same distance between the adjacent support and catch threadsover an entire width of the warp.
 3. The process according to claim 1comprising the additional step of feeding the support threads to theedges of the warp from separate sectional warp beams, onto which thesupport threads have been wound as a yam sheet.
 4. The process accordingto claim 1 comprising using 10 to 40 threads on each edge of the warp assupport threads.
 5. The process according to claim 1 comprising usingsupport threads having a hot-air shrinkage of 1% to 4%, measured at 190°C.
 6. The process according to claim 5 comprising using support threadshaving a hot-air shrinkage of 1% to 3%, measured at 190° C.
 7. Theprocess according to claim 1 comprising using support threads comprisingtwisted threads.
 8. The process according to claim 7 comprising usingsupport threads having 200 to 700 turns per meter.
 9. The processaccording to claim 7 comprising using support threads comprisingdouble-twisted threads.
 10. The process according to claim 6 comprisingusing support threads comprising double-twisted threads.
 11. The processaccording to claim 1 comprising using support threads having athread/thread friction between the weft and support threads of 20 to 70cN.
 12. The process according to claim 1, wherein the severing by fusioncomprises the additional step of adhering the ends of the weft threadsin the molten state to the threads at the edges of the remaining warp.13. The process according to claim 12, wherein the severing by fusioncomprises the additional step of fusing the ends of the weft threads inthe molten state with the threads at the edges of the remaining warp.14. Fabric producible according to one of claims 1 to 12.